Purpose: Tumor-infiltrating lymphocytes (TIL), in particular CD8⁺ T cells and CD20⁺ B cells, are strongly associated with survival in ovarian cancer and other carcinomas. Although CD8⁺ TIL can mediate direct cytolytic activity against tumors, the role of CD20⁺ TIL is poorly understood. Here, we investigate the possible contributions of CD20⁺ TIL to humoral and cellular tumor immunity.

Experimental Design: Tumor and serum specimens were obtained from patients with high-grade serous ovarian cancer. CD8⁺ and CD20⁺ TIL were analyzed by immunohistochemistry and flow cytometry. Immunoglobulin molecules were evaluated by DNA sequencing. Serum autoantibody responses to the tumor antigens p53 and NY-ESO-1 were measured by ELISA.

Results: The vast majority of CD20⁺ TIL were antigen experienced, as evidenced by class-switching, somatic hypermutation, and oligoclonality, yet they failed to express the canonical memory marker CD27. CD20⁺ TIL showed no correlation with serum autoantibodies to p53 or NY-ESO-1. Instead, they colocalized with activated CD8⁺ TIL and expressed markers of antigen presentation, including MHC class I, MHC class II, CD40, CD80, and CD86. The presence of both CD20⁺ and CD8⁺ TIL correlated with increased patient survival compared with CD8⁺ TIL alone.

Conclusions: In high-grade serous ovarian tumors, CD20⁺ TIL have an antigen–experienced but atypical CD27⁻ memory B-cell phenotype. They are uncoupled from serum autoantibodies, express markers of antigen-presenting cells, and colocalize with CD8⁺ T cells. We propose that the association between CD20⁺ TIL and patient survival may reflect a supportive role in cytolytic immune responses. Clin Cancer Res; 18(12); 3281–92. ©2012 AACR.